GaN-based materials have excellent properties for application in power transistors for low loss and high power switching. The AlGaN/GaN/AlGaN double-heterostructure FETs (DHFETs) configuration is extremely promising for high power applications due to the improved carrier confinement.
These devices offer lower on-resistance RON (due to the formation of 2-DEG in un-doped GaN-channel) and high breakdown voltage due to AlGaN buffer. Among the substrates (Si, SiC, sapphire), Si is the most suitable choice for epitaxial growth due to its comparable thermal conductivity to GaN system, low cost and large size availability. However, devices fabricated on Si have the disadvantage that the maximum breakdown voltage (VBD) is limited by the Si substrate itself due to its lower critical electrical field strength (0.3 MV/cm) compared to Al(GaN) materials. This leads to an unwanted leakage path across the AlN/Si inversion interface and therefore VBD is limited by the thickness of the buffer.